The present invention relates to a device for writing on card-shaped data memories with at least one magnetic strip that is positioned on the upper side or underside in the center or to the side. The device has a card slot in which at least two oppositely arranged write heads for writing on the at least one magnetic strip on the upper side or the underside of the card-shaped data memory are provided. At least one read head and at least one sensor arranged at one end of the card slot are also provided.
Such devices for writing on card-shaped data memories used in connection with vending machines and service machines are known, for example, from European Patent Application 0 521 172. In order to be able to write on the magnetic strip independent of the insertion direction of the card-shaped data memory into the card slot and independent of the correct positioning of the upper side and underside, it is suggested to use instead of one single write head two oppositely arranged write heads within the card slot. The paired, oppositely arranged write heads in the known device are activated simultaneously so that the magnetic strip is written on even when the insertion direction of the card-shaped data memory into the card slot is switched with respect to the upper side and underside.
In this arrangement of paired, oppositely arranged write heads there is a risk that the magnetic fields positioned opposite one another affect the simultaneously activated write heads to a greater or lesser extent so that the information written on the magnetic strip of the card-shaped data memory can be falsified.
It is therefore an object of the present invention to improve the device for writing on card-shaped data memories of the aforementioned kind, without impairing the simple handling by the user, such that a falsification of the information to be written on the magnetic strip due to mutual influences of the oppositely arranged write heads is prevented.